Structural studies and magnetic and transport properties of Cr-substituted La0.67Ba0.33Mn1−x Cr x O 3 (0≤ x ≤0.15) perovskites
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| Title: | Structural studies and magnetic and transport properties of Cr-substituted La |
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| Authors: | Oumezzine, Marwène1,2 marouan.omezzine@etudiant.univ-rennes1.fr, Peña, Octavio2, Kallel, Sami1, Guizouarn, Thierry2, Oumezzine, Mohamed1 |
| Source: | Journal of Alloys & Compounds. Aug2012, Vol. 533, p33-40. 8p. |
| Subjects: | Magnetic properties of metals, Transport theory, Chromium compounds, Perovskite, X-ray spectroscopy, Semiconductor doping, Electric conductivity |
| Abstract: | Abstract: We have investigated the structural, magnetic and electrical transport properties of a series of ABO3-type perovskite compounds, La0.67Ba0.33Mn1−x Cr x O 3 (0≤ x ≤0.15), which strongly depend on the doping level x. The slight difference between the ionic radii of Cr3+ and Mn3+ causes no change in the structure when x ≤0.1, remaining rhombohedral (space group R-3C), while for x =0.15 the structure becomes cubic (space group Pm-3m). Energy dispersive X-ray analysis (EDAX) confirms the expected stoichiometry of all samples. Upon Cr doping on the Mn site, the lattice parameters, the unit cell volume and the Bh name="sbnd" />B bond angle are reduced. All samples present a single magnetic transition from ferromagnetic to paramagnetic phase, showing a decrease of the Curie temperature T c and the magnetization M when x increases (x ≤0.15). However, Cr doping makes the saturation magnetization at 5K to decrease, which indicates that the Cr3+ moments tend to be antiparallel to the Mn3+ moments at low temperature. The Cr-doped manganites exhibit a large variation in resistivity values. The increase of Cr doping (x ≤0.15) leads to an increase of the electrical resistivity. Below 10at.% of Cr3+, the electrical resistivity shows a metallic behavior, which is well fitted by the relation ρ = ρ 0 + ρ 2T2 + ρ 4.5T4.5, indicating the importance of the grain/domain boundary, the electron–electron scattering effects and, to a lesser extent, the electron–(magnon, phonon) scattering effects in the mechanism of conduction. On the other hand, the 15at.% of Cr3+ doping makes the material to exhibit a semiconductor behavior, for which the electronic transport can be explained by a variable range hopping (VRH) and small polaron hopping (SPH) models. Results are consistent with a reduction of the number of available hopping sites for the Mn e g (↑) electron due to the substitution of Mn3+ by Cr3+, which suppresses the double exchange (DE) interactions. [Copyright &y& Elsevier] |
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| Database: | Engineering Source |
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